A military staff (often referred to as General Staff, Army Staff, Navy Staff or Air Staff within the individual services) is a group of officers and enlisted personnel that are responsible for the administrative, operational and logistical needs of its unit. It provides bi-directional flow of information between a commanding officer and subordinate military units. A staff also provides an executive function where it filters information needed by the commander or shunts unnecessary information.

One of the key purposes of a military staff is to provide accurate, timely information (which includes the results of contingency planning) on which command decisions are based. A goal is being able to suggest approaches or help produce well-informed decisions that will effectively manage and conserve unit resources.

In addition to generating information, the staff also manages the flow of communication within the unit and around it. While controlled information flow toward the commander is a priority, those useful or contingent in nature are communicated to lower-level units and/or through their respective staffs. If the information is not pertinent to the unit, it is redirected to the command level which can best utilize the condition or information.

Staffs are generally the first to know of issues that affect its group. Issues that require major decisions affecting the unit's operational capability are communicated to the commanding officer. However, not all issues will be handled by the commander. Smaller matters that arise are given to a more appropriate tasker within the unit to be handled and resolved, which would otherwise be an unnecessary distraction for the Commanding Officer who already makes numerous decisions every day.

In addition, a staff aims to carefully craft any useful situations and utilize that information.

In a generic command staff, more seasoned and senior officers oversee staff sections of groups organized by the needs of the unit. Senior Enlisted Personnel task personnel in the maintenance of tactical equipment and vehicles. Senior Analysts are tasked with the finalizing of reports, and their enlisted personnel participate in the acquisition of information from subordinate staffs and units. This hierarchy places decision making and reporting under the auspices of the most experienced personnel and maximizes information flow of pertinent information sent out of the command overall, clarifying matters overall. This frees up the most senior members of the command at each level for decision making and issuing direction for further research or information gathering (perhaps requiring men to put their lives at risk to gather additional intelligence).

Operations staff officers also are tasked with battle planning both for offensive and defensive conditions, and issuing contingency plans for handling situations anticipated during the foreseeable future.

Prior to the late 18th century, there was generally no organizational support for staff functions such as military intelligence, logistics, planning or personnel. Unitcommanders handled such functions for their units, with informal help from subordinates who were usually not trained for or assigned to a specific task.

Prussia also adopted a similar system in the following years. Initially, the Prussian Army assigned a limited number of technical expert officers to support field commanders. Before 1746, however, reforms had added management of intelligence and contingency planning to the staff's duties. Later, the practice was initiated of rotating officers from command to staff assignments and back to familiarize them with both aspects of military operations, a practice that, with the addition of enlisted personnel, continues to be used.

After 1806, Prussia's military academies trained mid-level officers in specialist staff skills. In 1814, Prussia formally established by law a central military command—Prussian General Staff—and a separate staff for each division and corps.

Despite some professional and political issues with the Prussian system, their General Staff concept has been adopted by many large armies in existence today.

An exception to this is the U.S. military. While the U.S. armed forces have adopted the staff organizational structure described below, the General Staff concept has been largely rejected. This is partly due to U.S. concern that the professional members of General Staffs have historically demonstrated a tendency to lose touch with the operational forces they direct, and have occasionally come to regard their judgements as equal to, if not superior to, the civilian governments they nominally serve. The German General Staffs of both World Wars serve as examples of the down-side of the General Staff concept in implementation. The National Security Act of 1947 instead created a Joint Staff populated by military service members who, rather than becoming career staff officers on the German General Staff model, rotate into (and back out of) Joint Staff positions. Following the major revision of Title 10 of the United States Code by the Goldwater–Nichols Act in 1986, the Joint Staff of today works directly for the Chairman of the Joint Chiefs of Staff rather than the corporate Joint Chiefs of Staff, as they did from 1947 to 1986. Under this scheme, operational command and control of military forces are not the province of the Joint Staff, but that of Combatant Commanders, who report through the Chairman of the Joint Chiefs of Staff unless otherwise directed, to the Secretary of Defense.

Most NATO countries have adopted the continental staff system (also known as the general staff system) in structuring their militaries' staff functions. In this system, which is based on one originally employed by the French Army in the 19th century, each staff position in a headquarters or unit is assigned a letter-prefix corresponding to the formation's element and one or more numbers specifying a role.

The staff numbers are assigned according to custom not hierarchy, traceable back to French practice; i.e., 1 is not "higher ranking" than 2. This list reflects the SHAPE structure:[1]

Since the original continental staff system only covered branches 1 through 6, it is not uncommon to see 7 though 9 omitted or having various meanings.[3] Common variation include merging of 3 and 5 to 3, Operations and Plans; omitting the training branch and utilizing 7 for engineering (as seen in US Military Sealift Command[4] and Multinational Forces-Iraq (MNF-I)[5]) and replacing 9 with a legal-branch (making CIMIC a part of another branch, i.e. 2 or 4) as seen with the UK Permanent Joint Headquarters.[6]

Derived from the Prussian Große Generalstab (Great General Staff), traditionally these staff functions were prefixed by the simple "G", which is retained in place for modern army usage. But the increasing complexity of modern armies, not to speak of the spread of the "Staff" concept to naval and other elements, has demanded the addition of new prefixes. These element prefixes are:

G, for Army or USMC general staff sections within headquarters of organizations commanded by a general officer and having a chief of staff to coordinate the actions of the general staff, such as divisions or equivalent organizations (e.g., USMC Marine Aircraft Wing and Marine Logistics Group) and separate (i.e., non-divisional) brigade level (USMC MEB) and above ;[7]

S, for Army or USMC executive staff sections within headquarters of organizations commanded by a field grade officer (i.e., major through colonel) and having an executive officer to coordinate the actions of the executive staff (e.g., divisional brigades, regiments, groups, battalions, and squadrons; not used by all countries);[7]

On some occasions the letter E can also be observed, though it is not an official term. In that case it is for element and it will be used to identify a small independent element, that is a part of a non-staff organization, i.e. an E3 is an operational element on a logistics site or an E4 is a logistics element on a forward medical support site.

Thus, the personnel officer of a naval headquarters would be referred to as N1. In reality, in large organizations each of these staff functions will require the support of its own large staff, so N1 refers both to the office and the officer in charge of it. The continental staff system can be carried down to the next level: J1.3 (or J13—sometimes the dot-separator is omitted) is thus the operations officer of the personnel office of a joint headquarters, but the exact definition of the roles at this level may vary. Below this, numbers can be attached following a hyphen, but these are usually only positional numbers assigned arbitrarily to identify individuals (G2.3-2 could be the budget officer in the operations section of the intelligence department; A1.1-1-1 might simply be a receptionist).

The manpower or personnel officer supervises personnel and administration systems. This department functions as the essential administrative liaison between the subordinate units and the headquarters, handling personnel actions coming from the bottom up (such as a request for an award to be given to a particular soldier) or from the top down (such as orders being received from the army level directing that a particular soldier be reassigned to a new unit outside the command). In army units, this person is often called the Adjutant. The S1 also works with the postal mailing office. S-1 deals with awards and ranks as well.

The intelligence section is responsible for collecting and analyzing intelligence information about the enemy to determine what the enemy is doing, or might do, to prevent the accomplishment of the unit's mission. This office may also control maps and geographical information systems and data. At the unit level, the S2 is the unit's security officer, and the S2 section manages all security clearance issues for the unit's personnel. Other duties of the S2 often include intelligence oversight, anti-terrorism/force protection and physical security.

The operations office may include plans and training. The operations office plans and coordinates operations, and all things necessary to enable the formation to operate and accomplish its mission. In most units, the operations office is the largest of the staff sections and considered the most important. All aspects of sustaining the unit's operations, planning future operations, and additionally planning and executing all unit training, fall under the responsibility of operations. The operations office is also tasked with keeping track of the weekly training schedules. In most military units (i.e. battalion, regiment, and brigade), the operations officer carries the same rank as the executive officer (XO), but would obviously rank third in the unit's chain of command while the other staff officers are one rank lower. For example, in a battalion, the S3 would hold the rank of major (like the battalion XO), while the remaining staff officers are captains or lieutenants.

Acquisition or construction, maintenance, operation, and disposition of facilities.

Acquisition or furnishing of services.

Medical and health service support.

By NATO doctrine, the logistic staff is tasked with overseeing logistic aspects and principles, where the focus is that logistic support must be focused towards ensuring the success of the operation and prescriptions of elements such as responsibility and authority.[8] A logistic staff may be divided into sections based on branch or geographic area. Each section may in turn also be divided into tasks and roles. The size of the logistic staff can vary greatly, depending on the environment and complexity of operations. NATO in example work with a Multinational Joint Logistic Centre,[9] which exists outside of the force commander's staff, but runs as a separate entity/unit, with only a few logistic personnel in the commander's staff who act as liaisons.

The plans & strategy office is responsible for civil military operations (CMO) strategy planning. At the unit level, the S5 is the primary adviser to the Commander on the civilian-to-military and military-to-civilian impact of the mission/operation within the Host Nation's (HN) Area of Interest (AOI), Area of Operations (AO) or the Target area of Interest (TAOI). The G5 serves as the Mission Support Office (MSO) at the Division level and HHC for civil military plans and strategy.

The signal office directs all communications and is the point of contact for the issue of communications instructions and protocol during operations as well as for communications troubleshooting, issue, and preventative maintenance. Communications at this level is paired with digital as well as voice (radio, computer, etc.). At the unit level, S6 is also usually responsible for all electronic systems within a unit to include computers, faxes, copy machines, and phone systems.

The finance branch, not to be confused with Administration from which it has split, sets the finance policy for the operation. Operationally, the Administration and Finance may be interlinked, but have separate reporting chains.

Civil-Military Co-operation or Civil Affairs are the activities that establish, maintain, influence, or exploit relations between the military forces, the government or non-government civilian organisations and authorities, and the civilian populace in a friendly, neutral, or hostile area of operations in order to facilitate military operations and consolidate and achieve mission objectives. See Army FM 41-10.

GSO1 General Staff Officer (Grade 1). The chief of staff, ranked a lieutenant colonel or colonel. He was in charge of the General Staff Branch, responsible for training, intelligence, planning operations and directing the battle as it progressed. Most orders from the General Officer Commanding (GOC) were actually written up and signed by the GSO1.[10]

"The British did have staff officers as far back as the Crimean War working in these three cells but staff work was looked at with great disdain in the British Army and only became acceptable after the terrible hardships of the Crimean war, brought on by disorganization"[11] The General Staff in Britain was formed in 1905, and reorganized again in 1908. Unlike the Prussian staff system, the British Army was thought too small to support separate staff and command career streams. Officers would typically alternate between staff and command.[12] Beevor, Inside the British Army, says instead that the terrible cleavages between staff and line units caused by the enormous losses during First World War trench warfare meant that British senior officers decided that from thenceforth all officers would rotate between staff and line responsibilities, preventing the development of a separate general staff corps.

In the British system, "staff" are outranked by "command" officers. The staff cannot in theory (and largely in practice) say "no" to a subordinate unit; only the Commander has that ability. The principal staff officers at any HQ were always outranked by the subordinate commanders:

Lieutenant Colonels commanding battalions or units in a brigade outrank the Brigade Major and the Deputy Assistant Adjutant & Quartermaster General

Brigadiers commanding brigades in a division outrank the Colonel GS and Colonel AQ

Major Generals commanding divisions outrank the Brigadier GS and Assistant Adjutant General and Assistant Quartermaster General at a Corps HQ

This ensured a clear chain of command, and reinforced the idea that staff do not command, but exercise control on behalf of their commander. By contrast, in the American system, commanders are frequently outranked by staff officers. For example, within a battalion, the S3 is a major while company commanders are captains.

G branch (operations) plans and executes operations. The senior staff officer in Brigade HQ was a Brigade Major (BM, rank Major), who coordinated the HQ. While the BM was responsible for the entire HQ, he concentrated mainly on "G" operational matters. A deputy BM GSO III generally looked after non-operational matters. Under the BM were several GSO III (rank captain) officers:

Operations (the senior captain)

Intelligence

Liaison. The Liaison section often had several Lieutenants attached from the brigade's combat units.

Air

A branch handled all personnel matters: awards, postings, promotions, medical, chaplains, military police and so forth. There were usually one or two GSO III officers in A branch.

Q Branch handled logistics, supply, transport, clothing, maintenance. There was usually one GSO III officer, with a learner Captain or Lieutenant, and several advisors, all Captains:

BRASCO (Brigade Royal Army Service Corps Officer)

BOO (Brigade Ordnance Officer)

BEME (Brigade Electrical and Mechanical Engineer Officer)

A and Q branches might be combined under a DAA&QMG (Deputy Assistant Adjutant and Quartermaster General, rank Major).[12]

The combined "A" and "Q" staffs was headed by a Colonel AQ, who was assisted by an AA&QMG (Assistant Adjutant and Quartermaster General, rank Lieutenant Colonel).

Members of the G staff:

A GSO II, acting as deputy to the GSO I. He was responsible for the preparation of orders and instructions as directed by the GSO I; the general organization and working of the "G" office; detailing of duty officers at the Div HQ; coordinating arrangements for moving the Main HQ; details of movement by road in consultation with the DAAG and DAQMG; and general policy regarding HQ defence and the preparation and promulgation of HQ standing orders. (In an Armoured Division Headquarters, the GSO II was responsible for the Division Tactical HQ and the above duties were done by the GSO III (Operations).)

The GSO III (Operations) was the understudy to the GSO II; he maintained the situation map; prepared situation reports; supervised the acknowledgment register; maintained the command matrix; prepared orders for the move of the Orders Group; and prepared orders for the move of the Division's Main HQ.

The GSO III (Operations)(Chemical Warfare) was responsible for all matters dealing with Chemical Warfare that affected the division; coordinated courses; was responsible for the camouflage policy; maintained the war diary; prepared and maintained location statements; received and distributed codes, call sign lists and other signals information from the divisional signals; coordinated traffic control and organization of routes in the divisional forward area under the GSO II and APM; was understudy to the GSO III (Operations) on all matters less CW.

The GSO III (Intelligence) coordinated all intelligence training and work in the division; coordinated the collection and collation of information about enemy dispositions, methods and intentions; prepared daily intelligence summaries; coordinated interpretation of air photographs with the Army Photographic Interpretation Section (APIS); effected liaison with the APIS, the field security office and the Intelligence Officer, Royal Artillery (at CRA); and was responsible for briefing and handling of press correspondents.

The GSO III (Liaison) coordinated the work of the Liaison Officers, was responsible for the division information room and served as an understudy to the GSO III (Operations).